Non-isokinetic sampling probes are used to study the solids flux profiles in circulating fluidized beds (CFB). The circulating solid flowrate (and its distribution) is one of the most important parameters of industrial units. However, little work has been done on the comparison of sampling probes. Three different types of non-isokinetic sampling probes (90 degrees bend, small radius with circular opening and large radius with square opening) were studied and compared in a rectangular cross-section pilot-scale CFB column. The net solids flux profiles are obtained from the difference between upward and downward fluxes and averaged over the cross-section of the column. The mean net solid flux is then compared to the overall circulating solids flowrate. The results obtained show that the non-isokinetic probe yields accurate solids circulation values. Best results were obtained using the ’large radius’ probe.